'Input sequences' are a 'little language' for data that vary by
year. A $5,000 yearly loan after retirement might be entered as
0 retirement; 5000
in a text control. Some users don't want to master that language,
and would prefer a pop-up dialog for each vector field like this:

labels: value from-duration to-duration

controls: textctrl spinctrl spinctrl

with the 'controls' repeated for each of a variable number of
intervals. Alternatively, the 'controls' might be cells in a
grid control. The 'values' might be a floating-point number,
a constrained list of strings, or both: for example, a premium
field must accept 'minimum' as well as '12345.67'. Similarly,
a 'duration' could be an integer or a string like 'retirement'.